Let me give you a couple of examples...
Last week, a bunch of youths filmed themselves shooting a girl in the leg with an airgun using the video camera on their mobile phone, for a laugh.
On the way home from work the other day, some schoolkids were happily making themselves vomit over the bus-shelter seat, for a laugh.
It's only a tiny percentage of the youths in whole that do this sort of thing, but when you are sitting on a bus and don't know whether one or more of the kids drawing graffiti on the window behind your head are a part of that percentage or not, it can make you feel kinda paranoid.
Blair is playing up for the cameras at the moment, 'Yob culture' is all over the newspapers. It's not nearly as big a problem as it's made out to be, but it does need dealing with, and the more the papers popularise it, of course, the more people hear about it and think 'Hey, I could do some 'Slaphappy TV' with my mates!'. Stamping down on people is not the way to do it though, but it may be the only short-term fix.